Brake



y 1940. R. A. GOEF'FRICH ,207,173

BRAKE Filed July 6, 193'? 2 Sheets-Sheet 1 INVENTOR,

g @0004; 62 GOA'PFP/CH BY )UWM ATTORNEY.

Patented July 9, 1940 UNITED STATES BRAKE Rudolph A. Goepfrich, SouthBend, Ind., assignor to Bendix Products Corporation, South Bend, Ind., acorporation of Indiana Application July 6, 1937, Serial No. 152,054

14 Claims.

This invention relates to fluid pressure braking systems for motorvehicles.

Broadly the invention comprehends a fluid pressure braking system formotor vehicles embodying means for applying the brakes associated withthe rear wheels of the vehicle with a greater amount of braking efiectthan may be applied by the brakes associated with the front wheels ofthe vehicle.

An object of the invention is to provide a fluid pressure braking systemfor a motor vehicle operative to change the ratio of the braking effectbetween the brakes associated with the rear wheels of the vehicle andthe brakes associated with the front wheels of the vehicle.

Another object of the invention is to provide a fluid pressure brakingsystem for motor vehicles operative to automatically change the ratio ofthe braking efiect between the brakes associated with the rear wheels ofa vehicle and the brakes associated with the front wheels of thevehicle.

Another object of the invention is to provide a fluid pressure brakingsystem operative to automatically reduce proportionately the ratio ofthe braking effect of the brakes associated with the rear wheels of avehicle and the brakes associated with the front wheels of the vehicle.

Other objects of the invention will appear from the followingdescription taken in connection with the drawings forming a part of thisspecification, and in which- Fig. 1 is a diagrammatical illustration ofa fluid pressure braking system embodying the invention;

Fig. 2 is a longitudinal sectional view of the ratio changer;

Fig. 3 is a top plan view of the ratio changer;

Fig. 4 is a longitudinal sectional view illustrating a modified form ofthe ratio changer; and

Fig. 5 is a top plan view of the modification illustrated in Fig. 4.

Referring to the drawings for more specific details of the invention,Ill represents a fluid pressure producing device of conventional typeadapted to be actuated by a foot pedal lever I2 45 pivoted on a suitablesupport l4 and connected by a retractile spring IE to a fixed supportl8.

A fluid pressure delivery pipe or conduit suitably connected to thefluid pressure producing device ID has branches 22 and 24 connectedrespectively to fluid pressure actuated motors 26 arranged in pairs, onepair for actuating the brakes associated with the front wheels of avehicle and another pair for actuating the brakes associated with therear wheels of the vehicle;

and suitably connected in the fluid pressure delivery pipe or conduit 24for delivering fluid under pressure to the fluid pressure actuatedmotors associated with the front wheels of the vehicle is a ratiochanger 28, the purpose of which will hereinafter appear.

The brakes may be of conventional type each including a fixed support orbacking plate 30 adapted to be secured to an axle or to an axle housing,a rotatable drum 32 associated with the backing plate and adapted to besecured to a wheel, a pair of corresponding friction elements or shoes34 pivoted on the backing plate, and a motor corresponding to the motors26 mounted on the backing plate between the friction elements or shoes34 and operative to spread the shoes into engagement with the drum 32against the resistance of a retractile spring 36 connecting the shoes.

The ratio changer 28 includes a cylinder 38 having a small chamber 40and a large chamber 42 arranged concentrically to and opening directlyinto the smaller chamber and providing at its junction with the smallchamber an annular shoulder 44. The smaller chamber has a head 46provided with a concentric opening 48 normally closed as by a plug 50having thereon a concentric pin 52, the purpose of which willhereinafter appear, and arranged in the wall of 'the chamber adjacentthe head 46 is a port 54 connected as by a fitting 58 to the fluidpressure delivery pipe 20.

A head 58 fitted in the open end of the large chamber 42 has therein a.chamber 60 of smaller diameter than the chamber 40. The chamber 60 isconcentrically disposed to and in direct communication with the largechamber 42, and the chamber 60 has a frustro-conical portion 62communicating at its apex with a port 64 in the head 58. The port isconnected as by a suitable fitting 68 to the fluid pressure deliverypipe 24; and arranged in the wall of the chamber 60 is a port 68normally closed as by a bleeder screw 10.

A piston 12 reciprocable in the chambers 40, 42 and 60 includes a body14 fitted in the chamber 42. The body has a concentric part 16 of reduced diameter fitted in the chamber 40. This reduced part 16 providesat its junction with the body an annular shoulder 18 normally seated onthe annular shoulder 44 of the cylinder and also has a head having anextension 82 provided with a circumferential flange 84. A sealing cup 86seated on the head 88 embraces the extension 82, and the flange 84 onthe extension serves to retain the cup against displacement.

'nular shoulder 44 of the cylinder. has an extension 96 provided with acircumfer- The body 14 of the piston also has a concentric part 88 ofreduced diameter providing at its junction with the body an annularshoulder 90 and also has a head 92 fitted in the chamber 60. A spring 94sleeved on the reduced part 86 between the shoulder 90 and the head 58of the cylinder urges the piston to its seat on the an- The head 92ential groove 98 and a conical end I00 adapted to seat in the conicalportion 62 of the chamber 60 so as to close the port 54. A sealing cupI02 on the head 92 has a lip fitted in the groove 98 in the extension 96so as to retain the cup against displacement.

The piston 12 has therein a valve chamber I04 and an axial passage I06intercepted by a plurality of diametral passages I08 in the extension98. The valve chamber and the passages provide a communication betweenthe chamber 40 and the chamber 60, and this communication is controlledby a suitable valve. As shown, the

open end of the valve chamber I04 has secured therein a hollow plug IIOreceiving the pin 52 on the plug 50, and the inner end of the plug H0 iscounter-sunk to provide a valve seat H2 for a ball valve II4 urged toits seat by a spring H6.

The piston 12 has a longitudinal slot H8, and a screw I20 mounted in thewall of the cylinder has a part received by the slot so as to inhibitrotation of the piston within the cylinder. The piston also has a recessI22 adapted to register with an opening I24 in the wall of the cylinder,and a casing I26 mounted on the wall of the cylinder has therein aspring-presed plunger I28 provided with a head I30 reciprocable in theopening I24 and adapted to enter the recess I22 so as to lock the piston12 against movement. The plunger I28 is provided with a handle I32 bywhich it may be extracted from the recess I22, and a suitable lock I34is provided for retaining the plunger in both advanced and retractedpositions.

A modification of the ratio changer is illustrated in Figs. 4 and 5. Inthis modification a double diametral cylinder I36 includes a smallchamber I38 and a large chamber I40 arranged concentrically to and indirect communication with the smaller chamber and providing at itsjunction with the smaller chamber an annular shoulder I42. The smallchamber is closed by a head I44 and the chamber has in its wall adjacentthe head a port I46 adapted to be connected to the fluid pressuredelivery pipe or conduit 20. The large chamber I 40 is closed as by ahead I48 and has in its wall adjacent its head a port I50 adapted to beconnected to the fluid pressure delivery pipe 24.

A piston I52 reciprocable in the cylinder has on one end a head I54fitted in the large chamber I40. The head I54 has an extension I56provided with a circumferential slot I58 and a sealing cup I60 seated onthe head has a lip fitted in the slot so as to retain the cup againstdisplacement. The other end of the piston has a head I62 fitted in thechamber I38. The head .I62 has an extension I64 provided with acircumferential slot I66, and a sealing cup I68 seated on the head has alip fitted in the groove, and a spring I10 interposed between the cupand the head I44 normally retains the piston against the head I48. Theextension I64 also has a groove in its face in which is fitted a valveseat I12.

The piston I62 has an axial passage I14 intercepted by a transverse slotI16 in the end of the extension I56. This passage and slot provide acommunication between the chamber I38 and the chamber I40. A valve I18for controlling the communication has a slotted stem I reciprocable inthe passage and a head I82 for cooperation with the valve seat I12. Aspring I84 interposed between the valve I18 and the head I44 of thecylinder urges the valve toits seat, and the stem I80 of the valve isadapted .to cooperate ith the head I48 to move the valve from its seat.A plunger I86 mounted on the wall of the cylinder has a part I88 adaptedto engage and lock the piston against movement, and a spring-pressed pinI90 is adapted to cooperate with a plurality of notches in the plungerfor retaining the plunger in either locked or disengaged position.

Assuming that the system is installed substantially as illustrated anddescribed, and that the ratio changer 28 connected in the system isunlocked, under these conditions, upon depressing the foot pedal leverI2 the fluid pressure producing device I0 is actuated to displace fluidtherefrom through the fluid pressure delivery pipe 20 and its respectivebranches into the nuid pressure actuated motors 26, causing actuation ofthe motors, and this actuation of the motors results in movement of theshoes 34 into engagement with the drums 32 against the resistance of theretractile springs 36.

Fluid under pressure enters the chamber 40 of the ratio changer 28 byway of the port 54, and is displaced therefrom through the hollow plugIIO, past the valve II4, through the valve chamber I04, the passages I06and I08, into the chamber 60, and thence through the port 64 and fluidpressure delivery pipe 24 to the fluid pressure actuated motors 26 ofthe brakes associated with the front wheels of the vehicle.

When the pressure on the fluid in the chamber 40 exceeds the load on thespring 94 plus the pressure on the fluid in the chamber 60, the piston12 advances and the conical end I00 of the extension 96 on the head 92of the piston seats in the conical portion 62 of the chamber 60 andeffectively closes the port 64. During this movement of the piston 12,the valve H4 is moved to its closed position under the influence of thespring II6.

Upon conclusion of a braking operation, the foot pedal lever I2 isreleased and is automatically returned to its retracted position underthe influence of the retractile spring I6. As the foot pedal leverreturns to its retracted position, the fluid pressure producing deviceI0 returns to its position of rest. This results in release of pressureon the fluid in the system and, accordingly, release of pressure on thefluid in the ratio changer, whereupon the ratio changer returns to itsnormal position and the fluid in the fluid pressure actuated motors 26and the fluid pressure piping system connecting the motors to the fluidpressure device is returned to the fluid pressure device under theinfluence of the retractile springs 36 connecting the shoes 34 of therespective brake structures.

It may be noted that as the pressure in chamber 40 is reduced inreleasing the brakes, the ball II4 remains on its seat, and the pressurein chamber 60 remains relatively higher for an instant so that theplunger 12 is immediately withdrawn to open the port 84. I

In the modification of the invention, fluid under pressure enters thechamber I38 by way of the port I46 and is displaced therefrom past thevalve I18 through the axial passage I14 and passage I10 into the chamberI40, thence through port I50 and the fluid pressure delivery pipe to thefluid pressure actuated motors.

When the pressure on the fluid in the chamber I40 exceeds the load onthe spring I10 plus the pressure on the fluid in the chamber I38, thepiston I52 moves to the left and the valve I'I8 closes, and upon anincrease of pressure on the fluid in the chamber I38, exceeding thepressure on the fluid in chamber I40, the valve again opens to establishcommunication between the chambers I38 and I40 by way of the axialpassage II4. This action may be repeated, and the result is that achange in the ratio of effectiveness of the two sets of brakes isaccomplished. That is to say up until the time the spring I10 isovercome, the pressures in the chambers I38 and I40 are equal. When thespring I10 is overcome the pressure in I38 becomes higher than thepressure in I40 but thereafter maintains a uniform ratio thereto. Theaction in maintaining this uniform ratio is either a fluttering of thevalve as described above, or a restriction of the opening to maintaindifferential pressures.

Although this invention has been described in connection with certainspecific embodiments, the principles involved are susceptible ofnumerous other applications that will readily occur to persons skilledin the art. The invention is, therefore, to be limited only as indicatedby the scope of the appended claims.

Having thus described the various features of the invention, what Iclaim as new and desire to secure by Letters Patent is:

1. In a fluid pressure braking system, a pressure producing device, twosets of brakes operatively connected to the device, and a ratio changerconnected between the device and one of the sets of brakes comprising areciprocable member adapted to be subjected to opposing pressures, saidmember having a passage therethrough and a valve for controlling thepassage.

2. In a fluid pressure braking system, a pressure producing device, twosets of brakes operatively connected to the device, and a ratio changerconnected between the device and one of the sets of brakes comprising areciprocable member having heads of different areas adapted to besubjected to opposing pressures, said member having a passagetherethrough and valve mechanism for controlling the passage.

3. The combination defined by claim 1 in which the ratio changercomprisesa cylinder, a double end piston reciprocable therein having apassage therethrough, and a valve for controlling the passage.

4. The combination defined by claim 1 in which the ratio changercomprises a double diametral cylinder, a double end piston reciprocabletherein having a head complementary to the different diameters of thecylinder, said piston having a passage therethrough, and a valve forcontrol of the passage.

5. The combination defined by claim 1 in which the ratio changercomprises a cylinder having a small chamber and a large chamber, apiston having a small head movable in the small chamber and a large headmovable in the large chamber, said piston having a passage therethrough,and valve mechanism for controlling the passage.

6. The combination defined by claim 1 in which the ratio changercomprises a cylinder having a small chamber and a large chamber, adetachable head on the cylinder having therein a chamber *5:

of smaller diameter than the diameter of the small chamber of thecylinder, a piston reciprocable in the large chamber of the cylinderhaving oppositely disposed heads movable respectively in the smallchamber of the cylinder and the chamber in the detachable head, and acontrolled passage through the piston and its respective heads.

'7. The combination defined by claim 1 in which the ratio changercomprises a cylinder having one of its ends closed and its other endopen, a small chamber in the closed end of the cylinder and a largechamber in the open end of the cylinder, a detachable head on the openend of the cylinder having therein a chamber of smaller diameter thatthe small chamber of the cylinder, a piston reciprocable in the largechamber having oppositely disposed heads, one movable in the smallchamber of the cylinder and the other movable in the chamber in thedetachable head. and a controlled passage through the piston and heads.

8. The combination defined by claim 1 in which the ratio changercomprises a cylinder having one of its ends closed and its other endopen, a small chamber in the closed end of the cylinder having an inletport, a large chamber in the open end of the cylinder, a detachable headon the open end of the cylinder having therein a chamber of smallerdiameter than the small chamber of the cylinder and a discharge port, a,piston reciprocable in the large chamber having oppositely disposedheads, one movable in the small chamber of the cylinder and the othermovable in the chamber of the detachable head, a passage through thepiston and its respective heads, and valve mechanism for controlling thepassage.

9. The combination defined by claim 1 in which the ratio changercomprises a cylinder having one of its ends closed and its other endopen, a small chamber in the closed end of the cylinder having an inletport and a. large chamber in the open end of the cylinder, a detachablehead on the open end of the cylinder having therein a chamber of smallerdiameter than the small chamber of the cylinder and a discharge port, apiston reciprocable in the large chamber having oppositely disposedheads, one movable in the small chamber of the cylinder and the othermovable in the chamber of the detachable head, a plunger carried by thepiston for control of the discharge port, a passage through the piston,a spring-pressed valve controlling the passage, and a spring interposedbetween the piston and the detachable head.

10. The combination defined by claim 1 in which the ratio changercomprises a double diametral cylinder having one of its ends open andits other end closed, a detachable head on the open end of the cylinder,said cylinder having inlet and outlet ports, a piston reciprocable inthe cylinder having oppositely disposed heads movable respectively inthe complementary parts of the cylinder, said piston having a passagetherethrough, and a valve for controlling the passage.

11. The combination defined by claim 1 in which the ratio changercomprises a double diametral cylinder having one of its ends open andits other end closed, a detachable head on the open end of the cylinder,said cylinder having inlet and outlet ports, a piston reciprocable inthe cylinder having oppositely disposed heads movable respectively inthe complementary parts oi the cylinder, an extension on the pistonadapted. to seat on the detachable head, a spring interposed betweenthepiston and the closed end of sponsive means for opening and closingthe discharge port.

13. The combination defined by claim 1 in which the ratio changercomprises a double diametral cylinder and diflerential pressureresponsive means for opening and closing the valve controlling thedischarge passage.

14. The combination defined by claim 1 in which the ratio changercomprises a diflerential, pressure responsive means for progressivelymaintaining a constant ratio between the inlet and outlet pressures. I

RUDOLPH A. GOEPFRICH.

